Vehicle control apparatus

ABSTRACT

A vehicle control apparatus for a hybrid vehicle mounting a torque converter with a lock-up clutch in order to better accomplish good drivability as well as good gasoline mileage than conventional vehicle control apparatuses includes an engine, a motor generator, a torque convertor with the lock-up clutch, and a battery, and expands a lock-up region when the battery is not under a input/output limited state wider than when the battery is under the input/output limited state while the vehicle is being driven at least by the engine.

TECHNICAL FIELD

The present invention relates to a vehicle control apparatus.

BACKGROUND ART

In recent years, a hybrid vehicle is focused on as one type of vehicleof environment-friendly automobiles. The hybrid vehicle generallyprovides an internal combustion engine (hereinafter simply referred toas engine) powered by fuel such as gasoline or the like, and an electricmotor (hereinafter simply referred to as motor) powered by electricpower from a battery.

There is already developed an above mentioned type of a hybrid vehiclehaving mounted thereon a vehicle control apparatus comprising, forexample, an engine, a motor, a torque converter and an automatictransmission mechanism connected in series, additionally provided withthe battery and a control unit (for example, refer to Patent Document1).

The torque converter is a fluid-type converter using circulatinghydraulic oil, and is adapted to transmit output torque of the motor tothe automatic transmission mechanism. The torque converter is adapted toamplify a torque inputted thereto and output the amplified torque byoperation of the circulating hydraulic oil. Further, the torqueconverter is provided with a lock-up clutch for connecting anddisconnecting between the motor and the automatic transmissionmechanism.

The lock-up clutch is adapted to disconnect the automatic transmissionmechanism from the motor, when the engine or the motor is over-loadedwhile the vehicle is running, with the result that the torque converterstarts slipping to amplify the output of the engine or the motor.

On the other hand, the lock-up clutch is adapted to lock up the motorand the automatic transmission mechanism by connecting each other, whenthe engine or the motor is slightly loaded, with the result that thetorque converter stops slipping, thereby improving transmittingefficiency of the driving force transmission system and gasoline mileageof the vehicle.

The control unit determines whether or not a crossing point of a vehiclespeed and an accelerator opening degree at each moment is within aregion in which the lock-up clutch should be connected (hereinafterreferred to as lock-up region) in avehicle-speed-accelerator-opening-degree map, by referencing thepreliminarily set vehicle-speed-accelerator-opening-degree map. When thecontrol unit determines that the crossing point of a vehicle speed andan accelerator opening degree at each moment exists in the lock-upregion, the control unit connects the lock-up clutch.

The battery is adapted to charge electric power generated by the motoror to discharge electric power for driving the motor in accordance withoperating condition of the vehicle. The control unit is adapted tocalculate a residual electrical quantity of the battery (hereinafterreferred to as SOC (state of charge)) based on an accumulating value ofcharge current and discharge current of the battery.

The control unit is adapted to expand the lock-up region of thevehicle-speed-accelerator-opening-degree map, when the SOC of thebattery is large and the motor can generate large driving force. Thus,the control unit is adapted to raise a frequency of the lock-up clutchbeing connected in the torque converter, thereby improving transmittingefficiency of the driving force transmitting system and gasoline mileageof the vehicle. Additionally, the control unit is adapted to limitinput/output of the battery and use of the motor, in order to protectthe battery, when SOC of the battery is excessively large.

CITATION LIST Patent Literature

Patent Document 1: Japanese Patent Application Publication No.2005-24049

SUMMARY OF INVENSION Technical Problem

However, the control unit applied for the conventional vehicle controlapparatus limits use of the motor to protect the battery and expands thelock-up region of the map to improve gasoline mileage, when SOC isexcessively large. Therefore, the conventional vehicle control apparatusmay have a possibility to have the lock-up clutch connected when the useof the motor is limited.

When the lock-up clutch is connected during operation when the use ofthe motor is limited, there is a possibility that the lock-up clutch isconnected even when the engine rotational speed is low. When the lock-upclutch is connected during the engine rotational speed being low, atorque fluctuation of the engine caused by cyclic cylinder igniting ofthe engine and cyclic reciprocating of the piston is transmitted to aninput shaft of a transmission without passing through the torqueconverter. In this case, a torsional vibration due to the torquefluctuation of the engine occurs on the driving force transmittingsystem, thereby causing a problem that drivability is deteriorated dueto a muffled noise being generated in a vehicle interior. Therefore,there exists a problem that the conventional vehicle control apparatuscannot simultaneously achieve drivability and gasoline mileage.

The present invention has been made to overcome the previously mentionedconventional problems, and it is therefore an object of the presentinvention to provide a vehicle control apparatus for a hybrid vehiclemounting a torque converter with a lock-up clutch which can betteraccomplish good drivability as well as good gasoline mileage thanconventional vehicle control apparatuses.

Solution to Problem

To achieve the above object, a vehicle control apparatus according tothe present invention comprises an internal combustion engine, anelectric motor connected with the internal combustion engine, a torqueconverter arranged between the electric motor and driving wheels, thetorque converter having a lock-up clutch provided therein and a batterythat charges and discharges the electric motor, in which the lock-upclutch is operative to switch a transmission state between a disengagingstate where the electric motor is disconnected from the driving wheelsand an engaging state where the electric motor is connected with thedriving wheels, and a lock-up region is expanded in a case that thebattery is not under an input/output limited state compared with thelock-up region in a case that the battery is under the input/outputlimited state, during a time when the vehicle is driven at least by theinternal combustion engine.

In the present description, the disengaging state of the lock-up clutchmeans not only a state where the motor is completely disconnected fromthe driving wheels, but also a state where there is slipping between themotor and the driving wheels, i.e., what is called a half-clutch.Further, connecting state of the lock-up clutch means a state where themotor is completely connected with the driving wheels without slipping.

In the present description, an input/output limitation of the batterybears a generic reference to both of an input limit value which isdefined as a maximum electric power chargeable to the battery and anoutput limit value which is defined as a maximum electric powerdischargeable from the battery, calculated from the residual electricpower in the battery and a battery temperature.

In the present description, a state where the battery is under aninput/output limited state means a state where the vehicle controlapparatus suppresses the electronic motor and the battery from beingcharged or discharged. In this state, the battery may be overdischargedif the battery continues discharging to the motor, because electricpower to be supplied to the electronic motor exceeds an output limitvalue of the battery. Further, the battery may be overcharged if thebattery continues being charged, because electric power to be suppliedto the electronic motor exceeds an input limit value of the battery.This means that the vehicle control apparatus is adapted to be unable touse the motor when the battery is under the input/output limited state.

In the present description, a state where the battery is not under theinput/output limited state means a state where the vehicle controlapparatus allows the electronic motor and the battery to be charged ordischarged. In this state, the battery may not be overdischarged even ifthe battery continues discharging to the motor, because electric powerto be supplied to electronic motor does not exceed the output limitvalue of the battery. Further, the battery may not be overcharged evenif the battery continues to be charged, because electric power to besupplied to the electronic motor does not exceed the input limit valueof the battery. This means that the vehicle control apparatus is adaptedto be able to use the electronic motor when the battery is not under theinput/output limited state.

In the present description, a lock-up region means a region where thelock-up clutch is allowed to be locked in a lock-up diagram, theabscissa thereof denoting the vehicle speed while the ordinate thereofdenoting the accelerator opening degree.

By the construction as set forth in the above definition, the vehiclecontrol apparatus expands the lock-up region, when the battery is notunder the input/output limited state wherein the motor is allowed to beused, wider than the lock-up region when the battery is under theinput/output limited state wherein the motor is not allowed to be used.

The vehicle control apparatus according to the present invention expandsthe lock-up region when the motor can be used, so that even if there isgenerated the torque fluctuation in the engine in a low vehicle speedregion, the torque fluctuation can be mitigated by driving the motor.Accordingly, the vehicle control apparatus according to the presentinvention can prevent the drivability from being deteriorated due to themuffled noise being generated by the torque fluctuation of the engine,as observed in a conventional vehicle control apparatus wherein thelock-up region is expanded even in a case that the motor cannot be used.

Further, the vehicle control apparatus according to the presentinvention has an expanded lock-up region when the motor can be used,allowing the lock-up clutch to be used more frequently, therebyimproving a transmitting efficiency of the driving force transmittingsystem and gasoline mileage. Therefore, the vehicle control apparatuscan accomplish good drivability as well as good gasoline mileage byexpanding the lock-up region when the motor can be used.

Furthermore, the vehicle control apparatus according to the presentinvention determines whether or not the lock-up region is expanded basedon whether or not the battery is under the input/output limited state.Therefore, the vehicle control apparatus can determine whether or notthe lock-up region is expanded by correctly determining whether or notthe battery is under the input/output limited state when compared with aconventional vehicle control apparatus which determines whether or notthe lock-up region is expanded based on SOC. Therefore, the vehiclecontrol apparatus can securely achieve good drivability as well as goodgasoline mileage by preventing the lock-up region from being erroneouslyexpanded when the battery is under the input/output limited state thoughSOC of the battery is satisfied, as observed in a conventional vehiclecontrol apparatus.

The vehicle control apparatus expands the lock-up region wider as aninput/output limitation of the battery becomes larger in a case that thebattery is not under the input/output limited state, when the vehicle isdriven at least by the internal combustion engine.

By the construction as set forth in the above definition, the vehiclecontrol apparatus expands the lock-up region wider as the input/outputlimitation of the battery is larger when the motor can be used.Therefore, the vehicle control apparatus can increase the output torqueof the motor by supplying larger amount of electric power as the lock-upregion is expanded wider. Accordingly, the vehicle control apparatus cangenerate a high output torque from the motor in response to the torquefluctuation of the engine being generated in a lower vehicle speedregion, thereby preventing drivability of the vehicle from beingdeteriorated by the muffled noise being generated in the vehicleinterior due to the torque fluctuation of the engine.

The vehicle control apparatus according to the present inventionminimizes the lock-up region in a case that the battery is under theinput/output limited state, when the vehicle is driven at least by theinternal combustion engine.

By the construction as set forth in the above definition, the vehiclecontrol apparatus unlocks the lock-up clutch when the muffled noise isbeing generated due to the torque fluctuation of the engine at lowvehicle speed, because the lock-up region is minimized when the motorcannot be used. Therefore, in the vehicle control apparatus, theslipping is generated in the torque converter, so that the enginerotational speed can be increased to the extent that the muffled noiseis not generated, while maintaining the vehicle speed. Accordingly, thevehicle control apparatus according to the present invention can preventthe drivability from being deteriorated due to the muffled noise beinggenerated by the torque fluctuation of the engine, as observed in aconventional vehicle control apparatus wherein the lock-up region isexpanded even in a case that the motor cannot be used.

The vehicle control apparatus according to the present invention is soconstructed that the lock-up clutch has a slipping amount that can bedecreased as a residual electric power in the battery is decreased, whenthe vehicle is driven only by the electric motor.

By the construction as set forth in the above definition, the electricpower regenerated by the motor is increased when slipping amount in thelock-up clutch is small, so that the vehicle control apparatus canincrease electric power regenerated by the motor as SOC is decreased andthe battery has more charging margin. Therefore, the vehicle controlapparatus can maintain good regenerating efficiency of the motor, whileprotecting the battery.

The vehicle control apparatus maximizes the lock-up region when residualelectric power in the battery is less than a predetermined limit valueand the vehicle is driven only by the electric motor. Here, thepredetermined limit value is defined as a residual electric power belowwhich the lock-up clutch is desirable to be slipped to decreaseregenerating efficiency for protecting the battery when the motorregenerates electric power.

By the construction as set forth in the above definition, the vehiclecontrol apparatus maximizes the lock-up region when SOC is less than thepredetermined limit value wherein the lock-up clutch is engaged so thatthe battery can accept electric power regenerated by the motor.Accordingly, the slipping in the torque converter can be suppressed toimprove a regenerating efficiency of the motor.

The vehicle control apparatus further comprises an accelerator pedalthat sets an acceleration demand of a driver for at least one of theinternal combustion engine and the electric motor, and the lock-upregion is determined based on a vehicle speed and an opening degree ofthe accelerator pedal.

By the construction as set forth in the above definition, the vehiclecontrol apparatus can select one of two driving modes, one is to improvegasoline mileage by locking the lock-up clutch and another is to improvedrivability by unlocking the lock-up clutch based on an accelerationdemand of the driver and the vehicle speed, and can securely achievegood drivability as well as good gasoline mileage.

The vehicle control apparatus according to the present invention setsthe vehicle to a lower vehicle speed in a case that the lock-up regionis expanded. By the construction as set forth in the above definition,the vehicle control apparatus can improve gasoline mileage because thelock-up clutch can be locked at lower vehicle speed.

The vehicle control apparatus according to the present invention furthercomprises a clutch disposed between the internal combustion engine andthe electric motor, the clutch switching a transmission state between adisconnected state where the internal combustion engine and the electricmotor are disconnected from each other and a connected state where theinternal combustion engine and the electric motor are connected witheach other, and the vehicle control apparatus sets the clutch to thedisconnected state when the lock-up clutch is under the engaging statefor regenerating electric power by the electric motor.

In the present description, a disengaging state of the clutch arrangedbetween the engine and the motor means a state where the engine iscompletely disconnected from the motor. Moreover, an engaging state ofthe clutch between the motor and the engine means a state where theengine is securely connected with the motor without slipping of theclutch, as well as a state where slipping between the motor and theengine is allowed such as a half-clutch state.

By the construction as set forth in the above definition, the vehiclecontrol apparatus disconnects the engine from the driving forcetransmitting system when electric power is regenerated by the motor bylocking the lock-up clutch. Accordingly, the vehicle control apparatuscan disconnect the engine load from the driving force transmittingsystem from the driving wheels to the motor, so that the regeneratedenergy in the motor can be secured. Therefore, the vehicle controlapparatus can improve gasoline mileage by efficiently regeneratingelectric power from the motor.

Advantageous Effects of Invention

According to the present invention, there is provided the vehiclecontrol apparatus for a hybrid vehicle mounting a torque converter witha lock-up clutch which can better accomplish good drivability as well asgood gasoline mileage than conventional vehicle control apparatuses.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a skeleton diagram schematically showing a driving systemhaving mounted thereon a vehicle control apparatus according to anembodiment of the present invention.

FIG. 2 is a skeleton diagram schematically showing a main part of adriving system having mounted thereon the vehicle control apparatusaccording to the embodiment of the present invention.

FIG. 3 is a block diagram showing a control unit of the vehicle controlapparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart explaining the operation of the vehicle controlapparatus according to the embodiment of the present invention.

FIG. 5 is a time chart explaining the operation of the vehicle controlapparatus according to the embodiment of the present invention when thevehicle is under an EV running state where the vehicle is driven only bythe driving force of the motor.

FIG. 6 is a time chart explaining the operation of the vehicle controlapparatus according to the embodiment of the present invention when thevehicle is under an EHV running state where the vehicle is driven atleast by the driving force of the engine.

FIG. 7 is a graph showing a vehicle speed and accelerator opening degreemap applied for the vehicle control apparatus according to theembodiment of the present invention.

FIG. 8 is a graph showing the relationship between SOC and a slip amountof the lock-up clutch in the vehicle control apparatus according to theembodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The preferable embodiment of the vehicle control apparatus according tothe present invention will be described hereinafter with reference tothe accompanying drawings. The present embodiment is a case that thevehicle control apparatus according to the present invention is appliedto a driving system of a hybrid vehicle.

First, the construction of the driving system 1 will be explainedhereinafter.

As shown in FIGS. 1 to 3, the driving system 1 has provided therein anengine 10, a driving unit 20, an automatic transmission 30 and a controlunit 40. In the present embodiment, an engine side E and an automatictransmission side T are defined as the engine 10 side of the drivingsystem 1 and the automatic transmission 30 side of the driving system 1,respectively.

The engine 10 is constituted by a publicly known power unit whichoutputs driving force by combusting mixture gas of hydrocarbon fuel,such as gasoline or light oil and air in a combustion chamber not shown.The engine 10 constitutes an internal combustion engine of the presentinvention. The engine 10 is adapted to reciprocate pistons not shownarranged inside a cylinder block by iterating a cycle of intake,explosion and exhaust in a combustion chamber, so that a crank shaft 11connected to the pistons is rotated to transmit the driving force. Theengine 10 is adapted to transmit a torque from the crank shaft 11 to thedriving unit 20.

The crank shaft 11 has an engine rotational speed sensor 19 arranged inthe vicinity thereof. The engine rotational speed sensor 19 is adaptedto detect the rotational speed of the crank shaft 11 and to output asignal indicative of the rotational speed of the crank shaft 11 to thecontrol unit 40.

The driving unit 20 has provided therein an input portion 21, a clutch22, an one-way clutch 23, a motor generator 24, an output portion 27 anda casing portion 28. The motor generator 24 constitutes an electricmotor of the present invention. The driving unit 20 is arranged betweenthe engine 10 and the automatic transmission 30, and is adapted totransmit the driving force outputted from the crank shaft 11 of theengine 10 to a transmission input shaft 31 of the automatic transmission30 as explained hereinafter.

The input portion 21 has a clutch input shaft 212 provided therein. Theclutch input shaft 212 is coaxially arranged with the crank shaft 11.The clutch input shaft 212 is connected with the clutch 22 and theone-way clutch 23 to be integrally rotatable with each other, totransmit the driving force to the clutch 22 and the one-way clutch 23.

The output portion 27 provides a clutch output shaft 270. The clutchoutput shaft 270 is coaxially arranged with the clutch input shaft 212.The clutch output shaft 270 is connected with the clutch 22 and theone-way clutch 23 to be integrally rotatable with each other, and isadapted to transmit the driving force of the clutch 22 and the one-wayclutch 23 to an external unit. The clutch output shaft 270 is connectedto a transmission input shaft 31 of the automatic transmission 30 to beintegrally rotatable with each other, to transmit the driving forceoutputted from the driving unit 20 to the automatic transmission 30.

The motor generator 24 has a stator 240 and a rotor 241 providedtherein. The motor generator 24 is arranged on a driving forcetransmitting path between the crank shaft 11 and the transmission inputshaft 31.

The stator 240 has a stator core not shown and a three phase coil alsonot shown wound around by the stator core provided therein. The statorcore, for example, is formed by laminated magnetic steel sheets, and issecured to the casing portion 28. The stator 240 is adapted to generatea rotating magnetic field by supplying electric power to the three phasecoil.

The rotor 241 is arranged inside the stator 240 and has a plurality ofpermanent magnets embedded therein.

The rotor 241 has a motor rotational speed sensor 243 arranged in thevicinity thereof. The motor rotational speed sensor 243 is adapted todetect a rotational speed of the motor generator 24 by detecting arotational speed of the rotor 241 and to transmit a signal indicative ofthe rotational speed of the motor generator 24 to the control unit 40.

The motor generator 24 is adapted to work as an electric motor forrotating the rotor 241 by mutual action between a magnetic fieldgenerated by the permanent magnets embedded in the rotor 241 and arotating magnetic field generated by the three phase coil. The motorgenerator 24 is also adapted to work as a generator for generatingelectric power between both terminals of the three phase coil by mutualaction between a magnetic field generated by the permanent magnetsembedded in the rotor 241 and a rotation of the rotor 241.

The motor generator 24 is connected with an inverter 46. The inverter 46is connected with a battery 47. By this configuration, the motorgenerator 24 and the battery 47 are adapted to transfer electric poweramong each other through the inverter 46. The battery 47 is applied forcharging electric power generated by the motor generator 24 or fordischarging electric power depending on an operating condition of thehybrid vehicle.

An MG current sensor 461 is arranged on the power cable connecting theinverter 46 with the motor generator 24. The MG current sensor 461 isapplied for detecting a phase electric current through the power cableand for transmitting a signal indicative of the electric current to thecontrol unit 40. A battery voltage sensor 471 is arranged between theoutput terminals of the battery 47. The battery voltage sensor 471 isapplied for detecting the output voltage of the battery 47, and fortransmitting a signal indicative of the voltage to the control unit 40.A battery current sensor 472 is arranged on the output terminal of thebattery 47. The battery current sensor 472 is applied for detecting acharge and discharge current of the battery 47, and for transmitting asignal indicative of the charge and discharge current to the controlunit 40. A battery temperature sensor 473 is mounted on the battery 47.The battery temperature sensor 473 is applied for detecting temperatureof the battery 47, and for transmitting a signal indicative of thetemperature to the control unit 40.

The clutch 22 has equipped therein a multi-disc portion not shown and apiston portion also not shown. The clutch 22 is arranged between theinput portion 21 and the output portion 27. The clutch 22 is installedbetween the crank shaft 11 and the transmission input shaft 31, and isarranged to connect and disconnect the crank shaft 11 and thetransmission input shaft 31. This means that the clutch 22 is adapted toswitch the transmission state between the disengaging state in which theengine 10 is disconnected from the motor generator 24 and the engagingstate in which the engine 10 is connected with the motor generator 24.

The clutch 22 is a normally-open type. The clutch 22 is normally in thedisengaging state where the engine 10 is disconnected from the motorgenerator 24. Further, the clutch 22 is operated by a high pressurehydraulic oil supplied from an oil pump 34, as explained hereinafter, ofthe automatic transmission 30, to have the engine 10 and the motorgenerator 24 connected with each other. The clutch 22 is arranged on aninner peripheral portion of the motor generator 24.

The one-way clutch 23 is arranged between the crank shaft 11 and thetransmission input shaft 31, and is so connected to transmit only arotational power in a positive rotational direction from the crank shaft11 to the motor generator 24 through the transmission input shaft 31.Here, the positive rotational direction is defined as a rotationaldirection of the crank shaft 11. The one-way clutch 23 is installed inthe inner peripheral portion of the motor generator 24. The one-wayclutch 23 is arranged axially adjacent to the clutch 22 in the innerperipheral portion of the motor generator 24.

The clutch input shaft 212 has an input shaft speed sensor 29 arrangedin the vicinity thereof. The input shaft speed sensor 29 is adapted todetect the rotational speed of the clutch input shaft 212, and to inputa signal indicative of the rotational speed to the control unit 40. Theinput shaft speed sensor 29 may be a resolver, for example.

The automatic transmission 30 has provided therein the transmissioninput shaft 31, a torque converter 32, a transmission mechanism inputshaft 33, the oil pump 34, a transmission mechanism 35, a hydrauliccontrol unit 36, an output shaft 37 and a housing case 38. The automatictransmission 30 is connected with the motor generator 24.

The torque converter 32 is a hydraulic type employing circulatinghydraulic oil, and is adapted to transmit a driving force transmittedfrom the clutch output shaft 270 of the driving unit 20 to thetransmission mechanism 35 through the transmission input shaft 33. Thetorque converter 32 has provided therein a turbine runner 90, a pumpimpeller 91, a front cover 92, a stator 93, a one-way clutch 94, ahollow shaft 95 and a lock-up clutch 96. This means that the torqueconverter 32 is connected between the motor generator 24 and the drivingwheels, and has the lock-up clutch 96 provided therein.

The turbine runner 90 and the pump impeller 91 are arranged to be heldin a face-to-face relationship with each other, so that the turbinerunner 90 is positioned in the engine side E. The turbine runner 90 isconnected with the transmission mechanism input shaft 33 to beintegrally rotatable with the transmission mechanism input shaft 33. Thepump impeller 91 is connected with the transmission input shaft 31 to beintegrally rotatable with the transmission input shaft 31. Inside thehousing case 38 is supplied with the hydraulic oil.

Between the turbine runner 90 and the pump impeller 91 is arranged thestator 93 in an inner circumferential side of the turbine runner 90 andthe pump impeller 91. The stator 93 is connected with the hollow shaft95 through the one-way clutch 94. The hollow shaft 95 is secured to thehousing case 38 and has the transmission mechanism input shaft 33rotatably accommodated therein.

The lock-up clutch 96 provides a lock-up piston 96 a and a frictionmember 96 b fixed on the lock-up piston 96 a. The lock-up clutch 96 isadapted to be pressed towards the engine side E by the high pressurehydraulic oil discharged from the oil pump 34 controlled by thehydraulic control unit 36, as shown by dotted arrows in FIG. 2. Thelock-up piston 96 a is moved towards the engine side E by the hydraulicoil, so that the friction member 96 a is pressed against the front cover92.

The lock-up clutch 96 is adapted to be switched to the engaging state bythe lock-up piston 96 a sliding towards the engine side E. In theengaging state, the friction member 96 b is pressed against the frontcover 92, so that the friction member 96 b and the front cover 92 areconnected with each other by friction, with the result that the frontcover 92 is integrally rotated with the turbine runner 90. The lock-upclutch 96 is adapted to have the transmission input shaft 31 and thetransmission mechanism input shaft 33 integrally rotatable with eachother, so that there is not generated the slipping of the hydraulic oil,thereby making it possible to improve gasoline mileage.

The lock-up clutch 96 is adapted to be switched to the disengaging statein response to the lock-up piston 96 a being slid towards the automatictransmission side T. In the disengaging state, the friction member 96 bis spaced apart from the front cover 92, so that the friction member 96b and the front cover 92 are independently rotatable from each other.For this reason, the turbine runner 90 and the front cover 92 areindependently rotatable from each other. The lock-up clutch 96 isadapted to be switched between the disengaging state where thetransmission mechanism 35 is disconnected from the motor generator 24and the engaging state where the transmission mechanism 35 is connectedwith the motor generator 24. Further, the hydraulic control unit 36 andthe oil pump 34 collectively constitutes a lock-up clutch switchingmeans for switching the lock-up clutch 96 between the disengaging stateand the engaging state.

The oil pump 34 has a rotor 340, a hub 341 and a body 342 providedtherein. The hub 341 has a cylindrical shape, and connects the rotor 340with the pump impeller 91 so that the rotor 340 and the pump impeller 91are integrally rotatable. The body 342 is fixed on the housing case 38.By this construction, the driving force from the driving unit 20 istransmitted from the front cover 92 to the rotor 340 through the pumpimpeller 91, thereby making it possible to drive the oil pump 34.

The hydraulic oil discharged from the oil pump 34 is supplied not onlyto the transmission mechanism 35, but also to the clutch 22 in thedriving unit 20 as shown by the chain line in FIG. 2. The oil pump 34 isadapted to supply the hydraulic oil to change a gear stage or a gearratio of the transmission mechanism 35 and to connect the clutch 22.

Between the oil pump 34 and the clutch 22 is arranged a hydraulicpressure regulating valve 39. The hydraulic pressure regulating valve 39is adapted to regulate an amount of hydraulic oil supplied from the oilpump 34 to the clutch 22 in accordance with a control signal from thecontrol unit 40.

The oil pump 34 and the hydraulic pressure regulating valve 39collectively constitute a clutch switching means. The oil pump 34 andthe hydraulic pressure regulating valve 39 are adapted to switch theclutch 22 from the disconnecting state to the connecting state.

The transmission mechanism 35 has a plurality of clutches and brakes notshown provided therein. In the transmission mechanism 35, an optimumshift range is formed by switching between the engaging state and thedisengaging state of a plurality of clutches and a plurality of brakesby the pressure of the hydraulic oil supplied from the hydraulic controlunit 36 in accordance with running states of the hybrid vehicle. Forexample, a N (neutral) range, D (drive) range, R (reverse) range, M(manual) range (sequential range), 2^(nd) (second) range, L (low) range,B (brake) range, S (sport) range, and Ds (sport drive) range can benamed as the shift ranges of the transmission mechanism 35.

The transmission mechanism 35 is connected with a shift lever 51 bywhich a driver of the vehicle changes gear stage. The shift lever 51 hasa shift position sensor 52 mounted thereon. The shift position sensor 52is adapted to detect a position of the shift lever 51 and to transmit asignal indicative of the shift position to the control unit 40.

The driving force outputted from the transmission mechanism input shaft33 is transmitted to the output shaft 37 through the transmissionmechanism 35 for driving the driving wheels through a differential gearnot shown. This means that the motor generator 24 is connected with thedriving wheels. The transmission mechanism 35 of the present embodimentis constituted as a multi-stage type, however the transmission mechanism35 of the vehicle having mounted thereon the vehicle control apparatusaccording to the present invention is not limited to the multi-stagetype but may alternatively employ, for example, a continuous variabletransmission with a transmission clutch.

The control unit 40 comprises an electronic control unit for the hybridvehicle (hereinafter referred to as ECU) 41, an electronic control unitfor the engine (hereinafter referred to as engine ECU) 42, an electroniccontrol unit for the motor (hereinafter referred to as motor ECU) 43, anelectronic control unit for the battery (hereinafter referred to asbattery ECU) 44 and an electronic control unit for the transmissionmechanism (hereinafter referred to as transmission ECU) 45. The controlunit 40 constitutes a control means in the present invention.

The ECU 41 provides a CPU (Central Processing Unit) 410, a ROM (ReadOnly Memory) 411 for storing a processing program, a RAM (Random AccessMemory) 412 for temporarily storing data, a back-up memory 413, an inputport 414, an output port 415, and a communication port 416. The ECU 41is adapted to supervise the control of the hybrid vehicle.

The input port 414 of the ECU 41 is connected with the engine rotationalspeed sensor 19, the input shaft speed sensor 29, the motor rotationalspeed sensor 243, a vehicle speed sensor 50, an acceleration sensor 54,the shift position sensor 52, the MG current sensor 461, the batteryvoltage sensor 471, the battery current sensor 472, and the batterytemperature sensor 473.

The vehicle speed sensor 50 is adapted to detect running speed of thevehicle and to transmit a signal indicative of the vehicle speed to thecontrol unit 40. The accelerator sensor 54 is connected to anaccelerator pedal 53. The accelerator sensor 54 is adapted to detect adepressed amount of the accelerator pedal 53, and to transmit a signalindicative of the depressed amount of the accelerator pedal 53 to theECU 41. The ECU 41 is adapted to calculate an accelerator opening degreeAcc based on the signal indicative of the depressed amount of theaccelerator pedal 53 transmitted from the accelerator sensor 54.

The accelerator pedal 53 is adapted to set an acceleration demand of adriver for at least one of the engine 10 and the motor generator 24. Theaccelerator pedal 53 is adapted to set an acceleration demand of adriver and to operate the rotational speed of at least one of the engine10 and the motor generator 24, in response to being depressed by thedriver.

The ECU 41 is connected with the engine ECU 42, the motor ECU 43, thebattery ECU 44, and the transmission ECU 45 through the communicationport 416. The ECU 41 is adapted to exchange various control signals anddata with the engine ECU 42, the motor ECU 43, the battery ECU 44 andthe transmission ECU 45.

The engine ECU 42 is connected with the engine 10 and the ECU 41. Theengine ECU 42 is adapted to be inputted with signals from varioussensors which detect the operating condition of the engine 10 and tocontrol the engine 10 with a fuel injection control, an ignition controland an intake air amount control and the like in accordance with theinputted signals.

The engine ECU 42 is adapted to communicate with the ECU 41. The engineECU 42 is adapted to control the engine 10 with the control signals fromthe ECU 41, and to output data indicative of operating conditions of theengine 10 to the ECU 41 as needed.

The motor ECU 43 is connected with the inverter 46 and the ECU 41. Themotor ECU 43 is adapted to control the motor generator 24. The motor ECU43 is adapted to input signals necessary for controlling the motorgenerator 24. The signals necessary for controlling the motor generator24 include a signal from the motor rotational speed sensor 243 mountedon the motor generator 24, a signal detected by the MG current sensor461 indicative of the phase current flowing through the motor generator24 and the like. The motor ECU 43 is adapted to output a switchingcontrol signal to the inverter 46.

The motor ECU 43 is adapted to communicate with the ECU 41. The motorECU 43 is adapted to regulate a rotational speed and an output torque ofthe motor generator 24 by controlling the inverter 46 in accordance withcontrol signals from the ECU 41. The motor ECU 43 is adapted to outputdata indicative of the operating conditions of the motor generator 24 tothe ECU 41 as needed.

The battery ECU 44 is connected with the battery 47 and the ECU 41. Thebattery ECU 44 regulates the battery 47. The battery ECU 44 is adaptedto be inputted with signals necessary for regulating the battery 47. Forexample, signals necessary for regulating the battery 47 include asignal indicative of an inter-terminal voltage from the battery voltagesensor 471, a signal indicative of charge and discharge current from thebattery current sensor 472 and a signal indicative of batterytemperature from the battery temperature sensor 473 and the like.

The battery ECU 44 is adapted to communicate with the ECU 41. Thebattery ECU 44 is adapted to output data indicative of operatingconditions of the battery 47 to the ECU 41 as needed. The battery ECU 44is adapted to calculate SOC of the battery 47 for regulating the battery47 based on the accumulated value of charge and discharge currentdetected by the battery current sensor 472.

The battery ECU 44 is adapted to determine a predetermined limit valuefor SOC of the battery 47. The limit value is defined as a residualelectrical quantity preferable for slipping the lock-up clutch 96 toprotect the battery 47 when the battery is regenerated by the motorgenerator 24. The predetermined limit value is a threshold value to beapplied when the ECU 41 determines whether or not the battery 47 isovercharged by the motor generator 24.

The battery ECU 44 is adapted to determine an input limit value W_(in)and an output limit value W_(out) of the battery 47. The battery ECU 44is adapted to determine basic limit values of W_(in) and W_(out) basedon the temperature of the battery, and to determine correction factorsfor W_(in) and W_(out) based on SOC. The battery ECU 44 is adapted tofinally determine an input limit value W_(in) and an output limit valueW_(out) by multiplying the basic limit values by correction factors. Thebattery ECU 44 is adapted to calculate the input limit value W_(in) andthe output limit value W_(out) from SOC and the battery temperature withreference to an SOC battery temperature map for calculating the inputlimit value Wi and the output limit value W_(out) based on apreliminarily set relationship between SOC and the battery temperature.

Further, the battery ECU 44 is adapted to determine whether or not thebattery 47 is under the input/output limited state.

The ECU 41 is adapted to calculate electric power to be supplied to themotor generator 24 by the battery 47 on the basis of the vehicle runningstate such as the vehicle speed. The battery ECU 44 is adapted todetermine that the battery 47 is under the input/output limited state,for example, when the electric power to be supplied to the motorgenerator 24 by the battery 47 exceeds the output limit value W_(out) ofthe battery 47. On the other hand, the battery ECU 44 is adapted todetermine that the battery 47 is not under the input/output limitedstate, for example, when the electric power to be supplied to the motorgenerator 24 by the battery 47 falls below the output limit valueW_(out) of the battery 47.

The ECU 41 is adapted to calculate electric power to be charged to thebattery 47 by the motor generator 24 on the basis of the motorrotational speed N_(M). The battery ECU 44 is adapted to determine thatthe battery 47 is under the input/output limited state, for example,when the electric power to be charged to the battery 47 by the motorgenerator 24 exceeds the input limit value W_(in) of the battery 47. Thebattery ECU 44 is adapted to determine that the battery 47 is not underthe input/output limited state, for example, when the electric power tobe charged to the battery 47 by the motor generator 24 falls below theinput limit value W_(in) of the battery 47.

The transmission ECU 45 is connected with the automatic transmission 30and the ECU 41. The transmission ECU 45 is adapted to control thelock-up clutch 96 of the torque converter 32, and to change the gearstage of the transmission mechanism 35.

The transmission ECU 45 is adapted to communicate with the ECU 41. Thetransmission ECU 45 is adapted to perform the shift control to changethe gear stage of the transmission mechanism 35 in accordance with thesignal from the ECU 41. The transmission ECU 45 is adapted to transmitdata indicative of the operating condition of the transmission mechanism35 and the torque converter 32 to the ECU 41 as needed.

As set forth in foregoing definitions, the engine 10, the motorgenerator 24, the torque convertor 32 and the battery 47 constitute apart of the vehicle control apparatus according to the presentembodiment. The vehicle control apparatus according to the presentembodiment is adapted to expand the lock-up region in the case that thebattery 47 is not under the input/output limited state, wider than thelock-up region in the case that the battery 47 is under the input/outputlimited state, when the vehicle is driven at least by the engine 10,i.e., when the vehicle is in EHV running state. The vehicle controlapparatus according to the present embodiment is adapted to expand thelock-up region wider as the input/output limitation of the battery 47becomes larger, in the case that the battery 47 is not under theinput/output limited state, when the vehicle is driven at least by theengine 10, i.e., when the vehicle is in EHV running state.

The vehicle control apparatus according to the present embodimentminimizes the lock-up region, when the battery 47 is under theinput/output limited state while the vehicle is driven at least by theengine 10, that is, the vehicle is in EHV running state.

The vehicle control apparatus according to the present embodiment isadapted to set slipping amount in the lock-up clutch 96 smaller as SOCis decreased, while the vehicle is driven only by the motor generator24, i.e., when the vehicle is in EV running state. The vehicle controlapparatus according to the present embodiment is adapted to maximize thelock-up region, when SOC is smaller than a predetermined value while thevehicle is driven only by the motor generator 24, i.e., when the vehicleis in EV running state.

The vehicle control apparatus according to the present embodiment hasprovided therein the engine rotational speed sensor 19, the motorrotational speed sensor 243, the vehicle speed sensor 50, the motor ECU43, the battery ECU 44 and the ECU 41. The ECU 41 is adapted todetermine whether the vehicle is in EHV running state where the vehicleis driven at least by the engine 10 or the vehicle is in EV runningstate where the vehicle is driven only by the motor generator 24, forexample, by comparing the rotational speed N_(E) of the engine 10 withthe rotational speed N_(M) of the motor generator 24, when the vehiclespeed is larger than zero.

In addition, the vehicle control apparatus according to the presentembodiment has provided therein the lock-up clutch 96, a lock-up clutchswitching means, the clutch 22, and a clutch switching means. The ECU 41is adapted to switch the transmission state of the lock-up clutch 96 bycontrolling the lock-up clutch switching means. The ECU 41, which has aclutch flag arranged therein, is adapted to control the clutch switchingmeans by setting the clutch flag on/off, so that the clutch 22 isswitched.

Further, the vehicle control apparatus according to the presentembodiment has the accelerator pedal 53 and the accelerator sensor 54provided therein. The ECU 41 is adapted to determine the lock-up regionbased on the vehicle speed and an accelerator opening degree Acc.

The ROM 411 and backup memory 413 are respectively stored therein with aVS-Acc map for determining whether the lock-up clutch 96 is connected ordisconnected depending on the vehicle speed VS and accelerator openingdegree Acc, i.e., the lock-up region map, as shown in FIG. 7. The ECU 41is adapted to determine whether the lock-up clutch 96 is engaged ordisengaged based on the current vehicle speed and current acceleratoropening degree with reference to the VS-Acc map. Further, the vehiclecontrol apparatus according to the present embodiment is adapted tolower the vehicle speed when the lock-up region is to be expanded.

The ROM 411 and the back up memory 413 are respectively stored thereinwith an SOC-slip amount map for determining the slipping amount in thelock-up clutch 96 based on SOC, for example, as shown in FIG. 8. The ECU41 is adapted to determine the slipping amount in the lock-up clutch 96with respect to SOC, with reference to the SOC-slip amount map when SOCexceeds the limit value. In the present embodiment, the smaller the SOC,the smaller the slipping amount in the lock-up clutch 96. The SOC-slipamount map shown in FIG. 8 is only an example, and other maps may beapplied for a vehicle control apparatus according to the presentinvention.

Further, the vehicle control apparatus according to the presentembodiment is adapted to switch the clutch 22 to the disconnected statewhen the lock-up clutch 96 is switched to the engaged state to have theelectric power regenerated by the motor generator 24.

Next, the operation will be explained hereinafter.

In the present embodiment, it is assumed that the hybrid vehicle isrunning under EV running state or EHV running state. As shown in FIG. 4,the ECU 41 determines whether or not the vehicle is running under EVrunning state where the vehicle is driven only by the motor generator 24(Step S1). The ECU 41 determined that the vehicle is running under EVrunning state, for example, when the vehicle speed is not zero and theengine rotational speed N_(E) is not equal to the motor rotational speedN_(M).

When the ECU 41 determines that the vehicle is running under EV runningstate (Step S1: YES), the ECU 41 determines whether or not SOC exceedsthe limit value (Step S2). The ECU 41 may preferably be adapted to allowthe slipping of the lock-up clutch 96 during the time when regenerationis being performed by the motor generator 24 in order to avoid thebattery 47 from being overcharged, if SOC exceed the limit value. Forthis reason, when the ECU 41 determines that SOC exceeds the limit value(Step S2: YES), the ECU 41 allows the slipping of the lock-up clutch 96with an amount determined on basis of SOC, regardless of the setting atthe lock-up region (Step S3).

The relationship between SOC and the slipping amount in the lock-upclutch 96 is determined so that allowable slipping amount in the lock-upclutch 96 is decreased as SOC is decreased, for example, as shown in theSOC-slip amount map in FIG. 8.

The ECU 41 can increase electric power regenerated by the motorgenerator 24, because the ECU 41 reduces allowable slipping amount ofthe lock-up clutch 96 as SOC is decreased. Therefore, a regenerationefficiency of the motor generator 24 can be maintained, while protectingthe battery 47. The ECU 41 returns a control to a main routine, afterthe ECU 41 sets the slipping amount of the lock-up clutch 96.

The ECU 41 is preferably adapted to engage the lock-up clutch 96 whenregeneration is performed by the motor generator 24 when SOC does notexceed the limit value, because it is not necessary to protect thebattery 47 from being overcharged. Therefore, when the ECU 41 determinesthat SOC does not exceed the limit value (Step S2: NO), the ECU 41 isadapted to maximize the lock-up region (Step S4). In the presentembodiment, the ECU 41 determines the lock-up region as a region of highvehicle speed side of line A which is maximally shifted towards lowvehicle speed side as shown in FIG. 7.

For this reason, the ECU 41 can lock up the lock-up clutch 96 while thevehicle is running at low vehicle speed, for example, in all the gearstages of the transmission mechanism 35. Therefore, the ECU 41 can lockup the lock-up clutch 96 while running at any one of 1^(st)-8^(th) gearranges when the vehicle is provided with the transmission mechanism 35of eight stages, thereby making it possible to improve a regenerationefficiency of the motor generator 24.

Further, the ECU 41 is adapted to switch the clutch 22 to thedisconnected state as needed, when the motor generator 24 regenerateselectric power by switching the lock-up clutch 96 to the engaged state.Therefore, the ECU 41 can disconnect the engine 10 from the drivingforce transmission system ranging from the driving wheels to the motorgenerator 24, so that the regeneration energy of the motor generator 24can be secured. The ECU 41 returns the control to the main routine aftermaximizing the lock-up region.

The ECU 41 determines whether or not the battery 47 is in theinput/output limited state (Step S5), when the ECU 41 determines thatthe vehicle is not running under the EV running state (Step S1: NO). Theabove determination is performed by the battery ECU 44 based on acomparison between the input/output limit values W_(in) and W_(out) ofthe battery 47 and the actual value of charge and discharge of the motorgenerator 24.

The ECU 41 cannot use the motor generator 24, when the battery 47 isunder the input/output limited state. Therefore, the ECU 41 is adaptedto minimize the lock-up region (Step S6), when the ECU 41 determinesthat the battery 47 is under the input/output limited state (Step S5:YES). In the present embodiment, the ECU 41 sets the lock-up clutchregion as a region of high vehicle speed side of line B which ismaximally shifted towards high vehicle speed side as shown in FIG. 7.

Therefore, for example, the ECU 41 locks up the lock-up clutch 96 whilethe vehicle is running at any one of 5^(th)-8^(th) gear ranges in a casethat the transmission mechanism 35 is equipped with an eight-stagetransmission. Therefore, the ECU 41 disconnects the lock-up clutch 96,when there is a muffled noise being generated due to the torquefluctuation of the engine 10 when the vehicle is running at low speed.For this reason, there is a slipping generated in the torque convertor32, so that the ECU 41 can keep the engine rotational speed N_(E)sufficiently high not to generate the muffled noise, while keeping thevehicle speed. The ECU 41 returns the control to the main routine afterminimizing the lock-up region.

The ECU 41 can use the motor generator 24, when the battery is not underthe input/output limited state. Therefore, when the ECU 41 determinesthat the battery is not under the input/output limited state (Step S5:NO), the ECU 41 expands the lock-up region wider than the lock-up regionunder the input/output limited state (Step S7). The ECU 41 expands thelock-up region wider as the input/output limit values W_(in) and W_(out)are larger. In the present embodiment, the ECU 41 defines the lock-upregion to be a region in high vehicle speed side of a line C, which canbe shifted between line A and line B as shown in FIG. 7.

For this reason, the ECU 41 can reduce the torque fluctuation of theengine 10 by activating the motor generator 24 even if there is thetorque fluctuation generated in the engine 10 while the vehicle isrunning at a low speed, thereby making it possible to suppress thedrivability from being deteriorated due to the muffled noise in avehicle interior. Additionally, the ECU 41 can improve gasoline mileageof the vehicle by raising the transmitting efficiency of the drivingforce transmission system. The ECU 41 returns the control to the mainroutine after appropriately setting the lock-up region between themaximum lock-up region and the minimum lock-up region.

Operations in a case that the aforementioned hybrid vehicle is runningunder EV running state where the hybrid vehicle is driven only by themotor generator 24 and the engine 10 is stopped will be explainedhereinafter with reference to a time chart as shown in FIG. 5.

As shown in FIG. 5, a clutch flag is in off state, and therefore theclutch 22 is in disconnected state. The motor rotational speed N_(M) isa rotational speed required for EV running, and the engine rotationalspeed N_(E) is zero. SOC fluctuates in accordance with the running stateof the vehicle. In the present embodiment, SOC being larger than thelimit value SOC_(L) at time T₀ is gradually decreased to be equal to thelimit value SOC_(L) at time T₁, then SOC remains smaller than the limitvalue SOC_(L) from time T₁ to time T₂, and is gradually increased largerthan the limit value SOC_(L) from time T₂ to time T₃.

The ECU 41 controls the lock-up clutch 96 so that slipping is allowed,because SOC is larger than the limit value SOC_(L) between T₀ and T₁.Further, the ECU 41 gradually decreases the slipping amount of thelock-up clutch 96, because SOC gradually decreases between T₀ and T₁.

The ECU 41 keeps the lock-up clutch 96 under the engaged state betweenT₁ and T₂, because SOC is smaller than the limit value SOC_(L) betweenT₁ and T₂. The ECU 41 controls the lock-up clutch 96 so that slipping isallowed, because SOC is larger than the limit value SOC_(L) between T₂and T₃. Further, the ECU 41 gradually increases the slipping amount ofthe lock-up clutch 96, because SOC gradually increases between T₂ andT₃.

In the above-mentioned hybrid vehicle, an operation that the vehicle isrunning under EHV running state where the vehicle is driven at least bythe engine 10 is explained with reference to a time chart shown in FIG.6.

As shown in FIG. 6, a clutch flag is in on state, and the clutch 22 isin connected state. The motor rotational speed N_(M) and the enginerotational speed N_(E) are the same rotational speed required for EHVrunning. The input limit value W_(in) and the output limit value W_(out)of the battery 47 fluctuate in response to the running state of thevehicle.

Here, for simplification of explanation, both of an electric power to besupplied from the battery 47 to the motor generator 24 and an electricpower to be charged from the motor generator 24 to the battery 47 areshown in FIG. 6 as a predetermined standard electric power Ws. Here,from T₀ to T₁, the input/output limitation of the battery 47, W_(in) andW_(out), are larger than the standard electric power Ws and aregradually being decreased, then from T₁ to T₂, W_(in) and W_(out) aresmaller than the standard electric power W_(S), and then from T₂ to T₃,W_(in) and W_(out) are larger than the standard electric power W_(S),and are gradually being increased. Therefore, the battery 47 is notunder the input/output limited state from T₀ to T_(I), the battery 47 isunder the input/output limited state from T₁ to T₂, and the battery 47is not under the input/output limited state from T₂ to T₃.

The ECU 41 controls the lock-up region between the maximum region andthe minimum region, because the battery 47 is not under the limitingcondition from T₀ to T₁. Further the ECU 41 gradually reduces thelock-up region, because the input/output limit values W_(in) and W_(out)are gradually decreased from T₀ to T_(I).

The ECU 41 minimizes the lock-up region, because the battery 47 is underthe input/output limited state from T₁ to T₂. The ECU 41 controls thelock-up region between the maximum region and the minimum region,because the battery 47 is not under the input/output limited state fromT₂ to T₃. Further the ECU 41 gradually increases the lock-up region,because the input/output limit values W_(in) and W_(out) are graduallyincreased from T₂ to T₃.

On the other hand, when the engine 10 is suspending and the hybridvehicle is stopping for parking or the like, the clutch 22 stays underthe disconnected state, because the oil pump 34 is being suspended. Atthis time, the shift position of the transmission mechanism 35 ispositioned at a neutral position. Further, the hydraulic pressureregulating valve 39 is opened.

The motor generator 24 is supplied with electric power to start theengine 10 when the engine 10 is suspending and the hybrid vehicle isstopping for parking or the like. By supply of the electric power to themotor generator 24, the motor generator 24 starts to rotate the rotor241 thereof. The driving force of the rotor 241 is transmitted to theoil pump 34 through a transmitting path comprising the clutch outputshaft 270 and the torque converter 32.

Here, the driving force generated by the motor generator 24 is nottransmitted to the engine 10 even though the rotor 241 is rotating,because the clutch 22 and the one-way clutch 23 are disconnected.Further, the output shaft 37 of the transmission mechanism 35 is notrotated even though the transmission input shaft 33 of the transmissionmechanism 35 is rotated by the rotation of the torque converter 32,because the shift position of the transmission mechanism 35 is set atthe neutral position.

The clutch 22 is connected in response to the hydraulic oil dischargedfrom the oil pump 34 being supplied to the clutch 22, so that thedriving force of the rotor 241 is transmitted to the crankshaft 11through the input portion 21, thereby causing the engine 10 started.

When the vehicle starts running after the engine 10 is started, thedriving force generated by the engine 10 is transmitted to the automatictransmission 30 through a transmitting path including the crankshaft 11,the input portion 21, the clutch 22, the rotor 241 and the clutch outputshaft 270. As the oil pump 34 is driven by the driving force transmittedto the automatic transmission 30, the hydraulic oil is continuouslysupplied to the clutch 22, so that the connection of the clutch 22 ismaintained. At this timing, the shift position of the transmissionmechanism 35 is set to the forward stage or the reverse stage.Therefore, the driving force of the crankshaft 11 is transmitted to thedriving wheels through the automatic transmission 30, so that the hybridvehicle starts running.

On the other hand, when the engine 10 is suspending its operation andthe hybrid vehicle is stopping for parking and the like, the clutch 22remains in the disengaging state. When the vehicle is started only bythe driving force of the motor generator 24, the motor generator 24 iselectrified. When the motor generator 24 is electrified, the rotor 241of the motor generator 24 starts rotating. The driving force of therotor 241 is transmitted to the oil pump 34 through the transmittingpath comprising the clutch output shaft 270 and the torque converter 32.

The driving force generated by the motor generator 24 is not transmittedto the engine 10 even though the rotor 241 is rotated, because theclutch 22 and the one-way clutch 23 are kept in the disengaging state.In addition, the hydraulic pressure regulating valve 39 is closed, sothat the hydraulic oil discharged from the oil pump 34 is not suppliedto the clutch 22.

The transmission input shaft 33 of the transmission mechanism 35 isrotated in response to the rotation of the torque converter 32. At thistiming, the shift position of the transmission mechanism 35 is set tothe forward stage or the reverse stage. Therefore, the driving force ofthe crankshaft 11 is transmitted to the driving wheels through theautomatic transmission 30, so that the hybrid vehicle starts running.

As will be understood from the foregoing description, the ECU 41 of thevehicle control apparatus according to the present embodiment expandsthe lock-up region, when the vehicle is running under EHV state and themotor generator 24 can be used. Therefore, even though there isgenerated a torque fluctuation in the engine 10 at a low vehicle speedregion, the torque fluctuation can be mitigated by driving the motorgenerator 24. Accordingly, the vehicle control apparatus according tothe prevent invention can suppress drivability from being deterioratedcaused by the muffled noise in the vehicle interior due to the torquefluctuation in the engine 10 at the low vehicle speed region.

Further, the ECU 41 expands the lock-up region when the vehicle isrunning under EHV state and the motor generator 24 can be used.Therefore, gasoline mileage of the vehicle can be improved by improvingtransmitting efficiency of the driving force transmitting system.Accordingly, the vehicle control apparatus according to the presentinvention can simultaneously achieve good drivability as well as goodgasoline mileage by expanding the lock-up region when the motorgenerator 24 can be used.

Furthermore, the ECU 41 determines whether or not the lock-up region isexpanded based on whether or not the battery 47 is under theinput/output limited state. Therefore, the ECU 41 can reliably determinewhether or not the motor generator 24 can be used to determine whetheror not the lock-up region is expanded, thereby making it possible toprecisely realize a simultaneous achievement of good drivability andgood gasoline mileage.

Still further, the ECU 41 of the vehicle control apparatus according tothe present embodiment expands the lock-up region, as the input/outputlimitation of the battery 47 is increased when the vehicle is runningunder EHV state and the motor generator 24 can be used. By this reason,the ECU 41 is allowed to supply larger electric power to the motorgenerator 24 for generating higher output torque of the motor generator24 as the lock-up region is more widely expanded. Accordingly, the ECU41 can generate the higher output torque from the motor generator 24against the torque fluctuation in the engine 10 generated at the lowervehicle speed region, thereby making it possible to suppress drivabilityfrom being deteriorated caused by the muffled noise in the vehicleinterior due to the torque fluctuation at the low vehicle speed region.

Moreover, the vehicle control apparatus according to the presentembodiment minimizes the lock-up region when the vehicle is running inEHV state and the motor generator 24 cannot be used. Therefore, thevehicle control apparatus unlocks the lock-up clutch 96, when themuffled noise is generated due to the torque fluctuation of the engine10 at the low vehicle speed region. For this reason, there is generatedthe slipping in the torque converter 32, so that the ECU 41 can increasethe engine rotational speed N_(E) to the extent that there is notgenerated the muffled noise, while maintaining the vehicle speed.Accordingly, the ECU 41 can suppress drivability from being deterioratedcaused by the muffled noise being generated in the engine 10 due to thetorque fluctuation of the engine 10 at the low vehicle speed region.

The ECU 41 of the vehicle control apparatus according to the presentembodiment can increase the slipping amount of the lock-up clutch 96 asthe SOC becomes smaller as long as the SOC stays larger than thepredetermined limit value when the vehicle is in the EV running state,thereby making it possible to increase the regenerating electric powerof the motor generator 24. Accordingly, the ECU 41 can maintain theregenerating efficiency of the motor generator 24 while protecting thebattery 47.

The ECU 41 of the vehicle control apparatus according to the presentembodiment is adapted to lock up the lock-up clutch 96, so that thebattery 47 becomes chargeable, and to maximizes the lock-up region, whenthe SOC is smaller than the predetermined limit value while the vehicleis in EV running state. Accordingly, the ECU 41 can improve regeneratingefficiency of the motor generator 24 by suppressing the slipping frombeing generated in the torque converter 32.

Further, the ECU 41 of the vehicle control apparatus according to thepresent embodiment determines the lock-up region based on the vehiclespeed and the accelerator opening degree. Therefore, the ECU 41 canselectively determine whether to lock up the lock-up clutch 96 toimprove gasoline mileage or to unlock the lock-up clutch 96 to improvedrivability, based on the acceleration demand of the driver and thevehicle speed, so that the ECU 41 can simultaneously achieve drivabilityand gasoline mileage in a good balance.

The ECU 41 is adapted to set the vehicle to a lower vehicle speed in acase that the lock-up region is expanded. Therefore, the ECU 41 can lockup the lock-up clutch 96 when the vehicle is driven in a lower vehiclespeed, so that gasoline mileage can be improved in a lower vehicle speedregion.

The ECU 41 of the vehicle control apparatus according to the presentembodiment controls the lock-up clutch 96 in response to SOC in EVrunning state. However, the vehicle control apparatus according to thepresent invention is not limited to the above mentioned construction,and known method of controlling the lock-up clutch may be applied.

The ECU 41 of the vehicle control apparatus according to the presentembodiment minimizes the lock-up region when the battery 47 is under theinput/output limited state in EHV running state. However, the vehiclecontrol apparatus according to the present invention is not limited tothe above mentioned construction, and known method of determining thelock-up region may be appropriately applied to controlling the lock-upregion when the battery 47 is under the input/output limited state inEHV running state.

The vehicle control apparatus according to the present inventionprovides the clutch 22 between the engine 10 and the motor generator 24.However, the vehicle control apparatus according to the presentinvention is not limited to above mentioned construction, and the clutch22 between the engine 10 and the motor generator 24 may be omitted. Inthis case, the construction of the vehicle can be simplified.

The vehicle control apparatus according to the present inventionprovides only one motor generator 24. However, the vehicle controlapparatus according to the present invention is not limited to the abovementioned construction, and more than two motor generators may beprovided therein.

The vehicle control apparatus according to the present embodiment isprovided with the driving unit 20 in which the clutch 22 and the one-wayclutch 23 are arranged in tandem along an inner peripheral portion ofthe rotor 241. However, the vehicle control apparatus according to thepresent invention is not limited to the above construction, and may beprovided with a driving unit 20 in which the clutch 22 and the one-wayclutch 23 are arranged so as to overlap axially each other in the innerperipheral portion of the rotor 241.

As explained above, the vehicle control apparatus according to thepresent invention is useful for a hybrid vehicle comprising a torqueconverter with a lock-up clutch, because the vehicle control apparatusaccording to the present invention provides an advantageous effect tosimultaneously achieve good drivability and good gasoline mileage.

EXPLANATION OF REFERENCE NUNERALS

-   1: driving system-   10: engine-   20: driving unit-   22: clutch-   24: motor generator-   30: automatic transmission-   32: torque converter-   34: oil pump-   35: transmission mechanism-   40: control unit-   41: ECU-   42: engine ECU-   43: motor ECU-   44: battery ECU-   45: transmission ECU-   47: battery-   96: lock-up clutch

The invention claimed is:
 1. A vehicle control apparatus comprising: aninternal combustion engine, an electric motor connected with theinternal combustion engine, a torque converter arranged between theelectric motor and driving wheels, the torque converter having a lock-upclutch provided therein, and a battery that charges and discharges theelectric motor, wherein the lock-up clutch is operative to switch atransmission state between a disengaging state and an engaging state,and a lock-up region, in which the lock-up clutch is permitted to be inthe engaging state, is expanded in a case that the battery is not underan input/output limited state compared with the lock-up region in a casethat the battery is under the input/output limited state, during a timewhen the vehicle is driven at least by the internal combustion engine.2. The vehicle control apparatus as set forth in claim 1, wherein thelock-up region is expanded to be wider as an input/output limitation ofthe battery becomes larger in the case that the battery is not under theinput/output limited state, when the vehicle is driven at least by theinternal combustion engine.
 3. The vehicle control apparatus as setforth in claim 1, wherein the lock-up region is minimized in the casethat the battery is under the input/output limited state, when thevehicle is driven at least by the internal combustion engine.
 4. Thevehicle control apparatus as set forth in claim 1, wherein the lock-upclutch has a slipping amount that can be decreased as a residualelectric power in the battery is decreased, when the vehicle is drivenonly by the electric motor.
 5. The vehicle control apparatus as setforth in claim 4, wherein the lock-up region is maximized when theresidual electric power in the battery is less than a predeterminedthreshold value and the vehicle is driven only by the electric motor. 6.The vehicle control apparatus as set forth in claim 1, wherein thevehicle control apparatus further comprises an accelerator pedal thatsets an acceleration demand of a driver for at least one of the internalcombustion engine and the electric motor, and the lock-up region isdetermined based on a vehicle speed and an opening degree of theaccelerator pedal.
 7. The vehicle control apparatus as set forth inclaim 6, wherein the vehicle is set to a lower vehicle speed in a casethat the lock-up region is expanded.
 8. The vehicle control apparatus asset forth in claim 1, further comprising a clutch disposed between theinternal combustion engine and the electric motor, the clutch switchinga transmission state between a disconnected state where the internalcombustion engine and the electric motor are disconnected from eachother and a connected state where the internal combustion engine and theelectric motor are connected with each other, and the clutch is set tothe disconnected state when the lock-up clutch is under the engagingstate for regenerating electric power by the electric motor.
 9. Thevehicle control apparatus as set forth in claim 1, wherein (i) theelectric motor rotates integrally with the driving wheels in theengaging state, and (ii) the electric motor rotates independently of, orwith slip, with respect to the driving wheels in the disengaging state.